A METHOD AND A DEVICE AT AN ELECTRICAL INSTALLATION BOX

Abstract: A method and a device at an electrical connection box of electrically non-conducting material having an open side, a bottom, and sidewalls associated with the bottom and having several holes or hole notches for lead-through of electrical cables. An insert (10) of electrically conducting material is inserted in the connection box, and holes (12) are provided in the insert (10) in front of at least one of the holes. Thereafter a cover (13) of electrically conducting material is arranged over the open side of the connection box in electrical contact with the insert, and the insert (10) is electrically earthed.

Description: A METHOD AND A DEVICE AT AN ELECTRICAL INSTALLATION BOX Technical Field Electrical connection boxes are presently used to a great extent for mounting in walls and ceilings. The boxes are connected by means of protective tubing before finali¬ zing the walls and ceilings, so that the wiring between distribution boxes and connection boxes can be done after the walls are finalized. The connection boxes are pre¬ ferably of three types, namely ordinary connection boxes, device boxes and lamp boxes. The boxes are normally cylinder shaped with a bottom and an open side wall. The cylindrical sidewall or mantel wall is provided with holes for electrical wires. In some cases only notches for holes are provided, so that the holes may be finalized in connection with mounting only in positions which come into question for a certain use. Con- nection pieces protrude from the outside of the box at the holes or notches and are intended for receiving the protec¬ tive tubes. Tubes and boxes are commonly manufactured of plastic. Bar-lcerrrnmri nf the Invention In later times the question about oversensitivity to electricity has become increasingly urgent. A possible cause for such oversensitivity can be electrical fields, for example fields that occur in the vicinity of electrical conductors in wiring in walls and ceilings in ordinary buildings. In order to reduce the electrical field strength from such fields it is known to use shielded cable at wiring. This is possible at cleaning-up of existing installations as well as in new installations. As the connection boxes used today are of plastic the electrical fields around the connection boxes need not be shielded. CORRECTED Short Summary of the invention An object of the present invention is to obtain a re¬ duction of the electrical field strength in entire electri¬ cal installations, inclusive of the connection boxes. According to the invention it shall also be possible to achieve the object in current installations as well as in new installations. These objects are according to the invention achieved in that an insert of electrically conducting material is inserted in the connection box and in that a cover of electrically conducting material is arranged over the open side of the connection box in electrical contact with the insert. Both the insert and the cover are thereafter elect¬ rically connected to earth. The earth referred to here is preferably the protective earth commonly provided in buil¬ dings. The arrangement of an insert in the connection box shall not according to the invention limit the possibili¬ ties for wiring to the inner space of the connection box, for which reason the insert is provided with holes or hole notches, which by correctly installing the insert in the connection box lie in front of the holes or hole notches in the connection box. Other advantages and features of the invention appear from the following description in combina- tion with the attached claims. Brief Description of the Drawings The invention will be further described by means of embodiments under reference to the attached drawings, in which Fig 1 shows an insert according to the invention with a cover belonging thereto, Fig 2 is a perspective view of a conventional connec¬ tion box for use together with the insert according to the invention, Fig 3 is a top view of an insert according to the in¬ vention, Fig 4 is a section along the line IV-IV in Fig 3, Figs 5 and 6 show an alternative embodiment of the insert according to the invention, and Figs 7 and 8 show another alternative embodiment of the insert according to the invention. Detailed Description In the embodiment shown in Fig 1 an insert according to the invention is designed as a cylindrical cup with a bottom 15. A side wall 16 is peripherally connected to the bottom 15. Several holes 12 are arranged in the sidewall 16, and the disposal of the holes in the insert corresponds to the disposal of connection pieces of the electrical con- nection box in which the insert is to be arranged. A con¬ ventional electrical connection box is described below under reference to Fig 2. The insert according to Fig 1 is to be mounted in a connection box, which normally is provi¬ ded with screw attachment means at two diametrically oppo- sed places internally in the box. The insert 10 has two corresponding attachment means in the form of portions 17 extending radially inwardly from the mantle surface of the insert. In the shown example the portions 17 form a part of a flange 18 extending radially outwardly from the top of the insert. In the flange 18 two sections are cut out in diametrically opposing places and are thereafter folded in towards the center of the insert in order to form the por¬ tions 17. The insert according to Fig 1 is made of stamped plate, but other manufacturing methods and materials are also possible. The insert can for example be made of forged aluminium. Depending on choice of material and manufactur¬ ing methods the holes can be made in different ways, for example by punching or drilling. In certain cases it may be preferred not to provide holes in the sidewall in advance. In such cases the side- wall may instead be provided with notches, for example in the form of so called "knock outs". A box 10, which is provided with holes 12, can also on its mantle surface be wound with a band of for example conducting silicon mate¬ rial, which thus closes the protective shield. Fig 2 shows a conventional connection box, which is suitable for housing an insert 10 according to the inven- tion. The connection box 19 is conventionally designed with a bottom and a cylindrical wall attached thereto. Holes are arranged in the wall, and connection pieces 20 for re¬ ceiving electrical protective tubing extend out from the outside of the box at the holes. The holes in the connec- tion pieces have positions corresponding to the holes 12 in the insert 10. As mentioned above, the invention is also applicable to other types of connection boxes, for example device boxes and lamp boxes. At different types of installation boxes the bottom and/or the internal mantle surface is designed in different ways. Asymmetrical portions internally in the installation box 19 are preferably used for preventing mutual rotation between the insert 10 and the connection box 19. Fig 3, which is a top view of the insert 10 according to Fig 1, shows a protruding portion 14, which is designed with such dimensions that it is received in a corresponding recess in the bottom of the installation box. As the shape is rectangular, mutual rotation between the connection box and the insert is prevented. The protruding portion 14 also appears clearly in Fig 4, also showing the flange 18 clearly. As mentioned above, different types of connection boxes are designed with different inner mantle surfaces and bottoms. Figs 5 and 6 show an insert 10 according to the in¬ vention for use together with a device box. As appears in Fig 6, the number of holes in the insert and the position of the holes vary within the scope of the invention. Figs 7 and 8 show another embodiment of an insert ac¬ cording to the invention. Fig 7 is a top view from the open side of the insert. The embodiment according to Fig 7 of the insert according to the invention differs from the em¬ bodiments described above mainly in that the cylindrical wall has two diametrically opposed recesses 19. The reces¬ ses 19 have shapes and dimensions corresponding to internal tubing means of a lamp box for receiving screws or the like. As appears from Fig 8, the bottom of the insert 10 is substantially planar, so that the recesses 19 in this embo¬ diment cooperate in preventing mutual rotation between the insert and the connection box. Connection boxes usually have a box ring, which is arranged in an internal groove in the box. For use in such cases the box ring is removed, whereafter the flange 18 of the box insert will be received in this groove. It is within the scope of the invention to replace the cover 13, which above all is used at connection boxes, with an electrical switch or a corresponding part, which is attached in the box. In order to guarantee the shielding it may be necessary to separately connect this equipment with earth and not only with the insert.

Claims: CLAIMS 1. A method at an electrical connection box of elect¬ rically non-conducting material having an open side, a bottom and sidewalls associated with the bottom and having several holes or hole notches for lead-through of electri¬ cal cables, c h a r a c t e r i z e d in that an insert (10) of electrically conducting mate¬ rial is inserted in the connection box, that holes (12) are provided in the insert (10) in front of at least one of the box holes, that a cover (13) of electrically conducting material is arranged over the open side of the connection box in electrical contact with the insert, and that the insert (10) is electrically earthed. 2. A device at an electrical connection box of plas¬ tic material with an open side, a bottom, and sidewalls associated with the bottom and having several holes or hole notches for lead-through of electrical cables, c h a r a c- t e r i z e d in that an insert (10) , provided with a bottom and made of an electrically conducting material, is arranged in the connection box, so that the insert (10) covers the bottom and the sidewalls of the connection box, that the insert (10) is provided with holes or hole notches in front of the holes or hole notches in the con¬ nection box, that the open side of the connection box is covered with a cover (13) of electrically conducting material, and that the cover is electrically connected with the in¬ sert and with earth. 3. A device according to claim 2, c h a r a c t e r¬ i z e d in that the insert (10) has portions (14) protruding axially from the bottom for receiving corresponding recesses in the connection box for preventing mutual rotation of the insert relative the connection box. 4. A device according to claim 2, c h a r a c t e r¬ i z e d in that the insert (10) is made of die-cast alumi¬ nium. 5. A device according to claim 2, c h a r a c t e r¬ i z e d in that the insert (10) is made of pressed plate. 6. A device according to claim 2, c h a r a c t e r¬ i z e d in that the insert (10) is a circular cylindrical box with a circular bottom (15) and an open side opposite the bottom (15) .

Inventors: HAGBERG ROLAND, HAGBERG, ROLAND
Applicants: HAGBERG ROLAND, IDEALPLAST AB, HAGBERG, ROLAND
Application year: 1994
Main classification: H02G3
IPC codes: H02G3